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E. Coli Bacteria Produce Toxic Protein to Ward Off Other Bacteria

NOV 20, 2017 | EINAV KEET
Can Escherichia coli (E. coli) bacteria communicate with each other and even other pathogens? According to one new study, by producing certain toxic proteins they can.

Although E. coli bacteria naturally reside in our intestines, pathogenic strains of the bacteria can cause diarrheal illness. When ingested, food or water contaminated with human or animal feces containing the bacteria can cause severe stomach cramps, diarrhea, and vomiting. The Centers for Disease Control and Prevention (CDC) monitors food-borne E. coli outbreaks, caused by food products such as beef, cheese, fresh spinach, and raw sprouts. Last year, researchers reported the discovery of a strain of E. coli harboring the mcr-1 gene for colistin resistance, giving the strain near pan-resistance to last-resort antibiotics.

Giving new insight into the vast survival capabilities of tiny E. coli bacteria is a recent study led by researchers from the Department of Energy’s Argonne National Laboratory, operated by the University of Chicago, as well as the University of California, Santa Barbara, and the University of California, Irvine. The study, published in the journal Nucleic Acids Research, details the authors’ work determining the molecular structures of toxic proteins the bacteria produce and release in their own social network to antagonize other neighboring bacteria and inhibit competitors. The protein, known as contact-dependent growth inhibition (CDI) toxin, is used by the NC101 strain of E. coli for intercellular competition. The study identified the protein structures of a 3-part system made up of a CDI toxin, its immunity protein, and its elongation factor.

The authors note that researchers have long known that bacteria can wage turf wars by producing antibiotics to fight off other bacteria. What is still unknown is whether the toxin is used to compete with and talk to other bacteria, or if its purpose is to control or kill neighbors.

“We are basically learning how the bacteria interact and communicate,” said study author Andrzej Joachimiak, PhD, in a recent news release from the University of Chicago. “We have some ideas that we are trying to resolve, because the toxins may have different activities. They may affect different bacteria differently.”

“These systems are found not only in soil and gut bacteria, but also in human pathogens,” said Dr. Joachimiak. “Some of these toxins of CDI systems are present in Pseudomonas aeruginosa, for example, which is involved in lung disease.”

The results of this new study could help with the development of new ways for humans to fight bacterial pathogens such as pneumonia and food-borne illnesses, important in light of a lack of new antibiotics in the pipeline.
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